Method for co-packaging light engine chiplets on switch substrate

ABSTRACT

A co-packaged optical module includes a substrate, a processor arranged on the substrate and a plurality of light engines mounted around the processor on the substrate using mounting assemblies configured to attach the respective light engines to the substrate. The light engines and the mounting assemblies are disposed along a perimeter of the substrate, including at corners of the substrate. Each of the mounting assemblies includes a socket, a metal clamp clamping a corresponding one of the light engines into the socket, and a plurality of pins which when mated with corresponding holes in the substrate cause peripheries of the mounting assemblies, including the light engines, the sockets and the metal clamps, to be flush with the perimeter of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/894,622, filed Jun. 5, 2020. The entire disclosure of the applicationreferenced above is incorporated herein by reference.

This application is commonly assigned to MARVELL TECHNOLOGY CAYMAN Iwith U.S. application Ser. No. 16/894,597, U.S. Attorney Docket No.MP9209, filed concurrently on Jun. 5, 2020, and U.S. application Ser.No. 16/894,611, U.S. Attorney Docket No. MP9210, filed concurrently onJun. 5, 2020, which are incorporated by reference herein for allpurposes.

BACKGROUND OF THE INVENTION

The present invention relates to optical telecommunication techniques.More particularly, the present invention provides a method forco-packaging multiple light engine chiplets with a switch processor on asingle switch substrate with minimum length of interconnect, a switchmodule having the co-packaged optics, and a method for unpackaging thelight engine chiplet.

As science and technology are updated rapidly, processing speed andcapacity of the computer increase correspondingly. The communicationtransmission or reception using the traditional cable is limited tobandwidth and transmission speed of the traditional cable and massinformation transmission required in modern life causes the traditionalcommunication transmission overload. To correspond to such requirement,the optical fiber transmission system replaces the traditionalcommunication transmission system gradually. The optical fibercommunication is chosen for systems requiring higher bandwidth andlonger distance that electrical cable cannot accommodate. Presentelectronic industrial performs research toward optical transmissionwhich will become the mainstream in the future even for short distancecommunication. Said optical communication is a technology in that lightwave functions as signal carrier and transmitted between two nodes viathe optical fiber. An optical communication system includes an opticaltransmitter and an optical receiver. By the optical transceiver, thereceived optical signal can be converted to an electrical signal capableof being processed by an IC, or the processed electrical signal can beconverted to the optical signal to be transmitted via optical fiber.Therefore, objective of communication can be achieved.

Over the last few decades, the use of communication networks exploded.In the early days Internet, popular applications were limited to emails,bulletin board, and mostly informational and text-based web pagesurfing, and the amount of data transferred was usually relativelysmall. Today, Internet and mobile applications demand a huge amount ofbandwidth for transferring photo, video, music, and other multimediafiles. For example, a social network like Facebook processes more than500 TB of data daily. With such high demands on data and data transfer,existing data communication systems need to be improved to address theseneeds.

40-Gbit/s and then 100-Gbit/s data rates wide-band WDM (WavelengthDivision Multiplexed) optical transmission over existing single-modefiber is a target for the next generation of fiber-optic communicationnetworks. More recently, optical components are being integrated onsilicon (Si) substrates for fabricating large-scale silicon photonicsintegrated circuits that co-exist with micro-electronic chips.Chip-scale lasers packaged directly within silicon photonicsopto-electrical system have been of interest for many applications suchas wide-band DWDM or CWDM communication and wavelength-steered lightdetection. A whole range of photonic components, including filters,(de)multiplexers, splitters, modulators, and photodetectors, have beendemonstrated, mostly in the silicon-on-insulator (SOI) platform. The SOIplatform is especially suited for standard DWDM communication bandsaround 1550 nm or CWDM communication band around 1310 nm, as silicon(n=3.48) and its oxide SiO₂ (n=1.44) are both transparent, and formhigh-index contrast, high-confinement waveguides ideally suited formedium to high-integration planar integrated circuits (PICs).

With the advances of optical communication technology and applicationsdriven by the market, the demands become stronger on increasingbandwidth for optical communication and decreasing package footprint ofan optical transceiver. It is more and more challenging to integrate allnecessary components within smaller and smaller module package. For thestate-of-art optical transceiver products, all the critical componentsincluding clock data recovery (CDRs), modulator drivers, transimpedanceamplifiers (TIAs), and PLC photonics blocks having optical passives,modulators, and photo detectors, are assembled side-by-side on a sameSOI-based component substrate in a 2D fashion. This approach has atleast two drawbacks for developing any future optical transceiver withdata rate greater than 400G. Firstly, the side-by-side placement of thecomponents consumes much of the board area for optical transceiver as apluggable product or major substrate area for on-board optics product,making it very difficult to further shrink the product size. Secondly,side-by-side placement on the substrate creates longer electricaltransmission length and often requires wire bonds between electrical dieand photonics die, introducing more electrical loss which damages signalintegrity for very high data rate transceiver product, e.g., >56 Gbaudsymbol rate. In particular, the wire bonds lead to impedance mismatchdue to large inductance, degrading the signal at higher frequencies. Assuch, it is not practical to use wirebond as electrical interconnectbetween chips or between chips and board for the applications where highfrequency (e.g., >40 GHz) analog signal is transmitted. The largeinductance of wire bonds has become a bottle neck of high-speed datatransmission.

To shorten the interconnect length of conventional wire bonds betweenelectronics devices (e.g., from modulator driver/TIA to digital signalprocessor DSP) or between electronics (driver/TIA) and photonics (e.g.,CDR and PAM4 ASIC), people have started to use through-silicon via (TSV)process and silicon interposer in Si photonics die to replace wire bondsand make interconnections. With the advancement of silicon TSVmanufacturing process for making Si photonics components and integratingactive components with wafer-level assembly and burn-in testing, aco-packaged optical-electrical system that assembles anoptical-electrical processor on a compact module substrate in very shortinterconnect length with multiple chiplet light engines would providegreat high-performance benefit and desired bandwidth capacity forvarious applications involving backplane reach, or medium reach, orshort reach, or extra-short reach interconnect switch for high-speeddata communication.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to optical telecommunication techniques.More particularly, the present invention provides a co-packagedoptical-electrical module with a switch processor and multiple lightengine chiplets mounted on a same switch substrate. Merely by example,the present invention discloses a light engine made from a photonicssub-module of multi-channel optical-electrical transceivers integratedon a single silicon photonics substrate in-packaged with multiple lasersto provide multiple CWDM channels carrying total 1.6 Tbit/s or highercapacity per light engine, a method for fixing a compact chiplet packageof the light engine on the switch substrate and releasing the chipletpackage therefrom, though other applications are possible.

In modern electrical interconnect systems, high-speed serial links havereplaced parallel data buses, and serial link speed is rapidlyincreasing due to the evolution of CMOS technology. Internet bandwidthdoubles almost every two years following Moore's Law. But Moore's Law iscoming to an end in the next decade. Standard CMOS silicon transistorswill stop scaling around 3 nm. And the internet bandwidth increasing dueto process scaling will plateau. But Internet and mobile applicationscontinuously demand a huge amount of bandwidth for transferring photo,video, music, and other multimedia files. This disclosure describestechniques and methods to improve the communication bandwidth beyondMoore's law.

In an embodiment, the present invention provides an in-packagedmulti-channel light engine. The in-packaged multi-channel light engineincludes four or more sub-assemblies of optical-electrical sub-modules.Each sub-assembly is assembled in a case formed with a lid membercovering a peripheral side member over peripheral edge region of asub-module substrate. Each optical-electrical sub-module includes atleast four laser chips, one or more driver chips, and one or moretrans-impedance amplifier (TIA) chips separately flip-mounted on asilicon photonics substrate and is coupled to an optical interface blockand an electrical interface block commonly mounted on the correspondingsub-module substrate. The in-packaged multi-channel light engine furtherincludes a first frame fixture with a crossly-joined bar across middleregion to form four or more window structures configured to allow thefour or more sub-assemblies to be fitted in respectively with topsurfaces of the lid members on top and bottom sides of the correspondingsub-module substrates at bottom. Additionally, the in-packagedmulti-channel light engine includes a second frame fixture configured tohold the first frame fixture with the four or more sub-assemblies. Thein-packaged multi-channel light engine further includes an interposerplate having a top side with four or more first-sets of conductingbumps, a bottom side with four or more second-sets of patternedconducting bumps, and a plurality of through-plate conducting vias andinterior conducting paths configured to connect the first-sets ofconducting bumps with the four or more second-sets of patternedconducting bumps. Each first-set of conducting bumps is configured tobond to a respective sub-module substrate. Furthermore, the in-packagedmulti-channel light engine includes a module substrate having a top sidewith four or more sets of conducting bump contacts configured torespectively bond to the four or more second-sets of conducting bumps.The in-packaged multi-channel light engine further includes a backplatemember attached to a bottom side of the module substrate. Moreover, thein-packaged multi-channel light engine includes a top plate memberconfigured to compress the second frame fixture that holds the firstframe fixture with the four or more sub-assemblies, the interposerplate, and the module substrate vertically together with the backplatemember. The top plate member is configured as a heatsink with aplurality of fin structures.

In a specific embodiment, the present invention provides a sub-assemblyof a multi-channel light engine. The sub-assembly includes a sub-modulesubstrate severed as a bottom member and a peripheral frame memberhaving four sides disposed along a peripheral region on a front surfaceof the sub-module substrate. The peripheral frame member has an openslot through at least one side. The sub-assembly further includes asilicon photonics substrate electrically bonded via through-substratevias bump contacts on the front surface of the sub-module substrate. Thesilicon photonics substrate is configured to fabricate multiple Si-basedwaveguide devices therein. Additionally, the sub-assembly includes oneor more driver chips, one or more transimpedance amplifier chips, andmultiple laser chips separately mounted on the silicon photonicssubstrate and coupled to corresponding Si-based waveguide devices toform a transmitter unit and a receiver unit. The sub-assembly furtherincludes an optical interface block containing multiple planarwaveguides formed on a glass substrate mounted on the front surface ofthe sub-module substrate next to the silicon photonics substrate. Themultiple planar waveguides are optically coupled to correspondingSi-based waveguide devices and optical fibers in a fiber cable laidthrough the open slot through the at least one side. The opticalinterface block is configured to deliver output transmitted from thetransmitter unit to an output optical fiber and to receive incomingmulti-wavelength light signal from an input optical fiber for thereceiver unit. Furthermore, the sub-assembly includes an electricalinterface block including multiple ASIC chips mounted on the frontsurface of the sub-module substrate or a back surface thereof andconfigured to receive data signals based on which control signals forthe laser chips are generated for producing multi-channel opticalsignals and process digital signals converted from the incoming lightsignal for electrical host. Moreover, the sub-assembly includes a toplid member covering the peripheral frame member to enclose the lightengine.

In an alternative embodiment, the present disclosure provides a packagedchiplet of a multi-channel light engine. The packaged chiplet includes alid member connected with a periphery member having one edge with anoptical connector port. Additionally, the packaged chiplet includes asub-module substrate having a peripheral region configured to beattached with the periphery member to form an enclosure with the lidmember. Furthermore, the packaged chiplet includes a first diecomprising an application-specific integrated circuit (ASIC) chipconfigured to at least serve as a digital signal processing (DSP)interface. Moreover, the packaged chiplet includes a second diecomprising a silicon photonics chip including Si-based waveguide devicescoupled to multiple laser chips to respectively provide multipledifferent wavelengths for multiple channels of an optical transceiver.The second die is electrically coupled and physically stacked with thefirst die in the enclosure.

In another alternative embodiment, the present disclosure provides aco-packaged optical-electrical module. The co-packagedoptical-electrical module includes a module substrate with a minimumlateral dimension no greater than 110 mm. Additionally, the co-packagedoptical-electrical module includes a main die with a processor chipdisposed at a central region of the module substrate. The processor chipbeing configured to operate with a digital-signal processing (DSP)interface for extra-short-reach or equivalent protocol datainterconnect. Furthermore, the co-packaged optical-electrical moduleincludes a plurality of chiplet dies disposed densely along a peripheralregion of the module substrate. Each chiplet die is configured to beself-packaged light engine on a sub-module substrate with a minimumlateral dimension to allow a maximum number of chiplet dies on themodule substrate with a distance of any chiplet die from the main diesmaller than 50 mm for extra-short-reach or equivalent protocol in datainterconnect operation.

In yet another alternative embodiment, the present disclosure provides apackaged light engine. The packaged light engine includes a sub-assemblyhaving a lid member connected with a periphery member configured as afront edge with an optical connector port, two opposing side edges withledge structures, and a back edge opposing to the front edge. Thesub-assembly further includes a sub-module substrate having a peripheralregion configured to support the periphery member to form an enclosurewith the lid member. Additionally, the sub-assembly includes a first diecomprising an application-specific integrated circuit (ASIC) chipconfigured to at least serve as a digital signal processing (DSP)interface. Moreover, the sub-assembly includes a second die comprising asilicon photonics chip including Si-based waveguide devices coupled tomultiple laser chips to respectively provide multiple differentwavelengths for multiple channels of an optical transceiver. The seconddie is electrically coupled and physically stacked with the first die inthe enclosure. The packaged light engine further includes an interposerpad disposed under the sub-module substrate. Additionally, the packagedlight engine includes a socket base member having a flat plate connectedto a peripheral wall structure having at least a front wall configuredwith at least two separated bottom notches and a back wall opposing tothe front wall with one connected bottom notch and two side wallsconnected to the front wall and the back wall. The flat plate isrecessed to receive the interposer pad and then the sub-module substrateas a part of the sub-assembly in an orientation with the opticalconnector port protruded out of a cutoff portion of the front wall.Moreover, the packaged light engine includes a shaped metal wire havinga horizontal backside section fitted in the connected bottom notch inthe back wall, two horizontal side sections pressed respectively on theledge structures within the two side walls, and two end sections lockedrespectively in the two separated bottom notches in the front wall, andseveral bended sections for connecting the horizontal backside section,the two horizontal side sections, and the two end sections and providingelastic forces on the ledge structures to clamp the sub-assembly in thesocket base member.

In still another alternative embodiment, the present disclosure providesa method for co-packaging multiple light engines in a switch module. Themethod includes a step of providing a module substrate with a minimumlateral dimension no greater than 110 mm. The module substrate isconfigured with a first mounting site at a center region and a pluralityof second mounting sites distributed densely along peripheral region ofthe module substrate. Additionally, the method includes a step ofdisposing a main die with a switch processor chip at the first mountingsite of the module substrate. The switch processor chip is configured tooperate with a digital-signal processing (DSP) interface forextra-short-reach or equivalent interconnect. Furthermore, the methodincludes a step of mounting a plurality of chiplet dies respectivelyinto the plurality of second mounting sites of the module substrate.Each chiplet die is configured to be a packaged light engine with aminimum lateral dimension to allow a maximum number of chiplet diesco-packaged on the module substrate with a distance of any chiplet diefrom the main die smaller than 50 mm for extra-short-reach interconnectoperation.

The present invention achieves these benefits and others in the contextof known waveguide laser modulation technology. However, a furtherunderstanding of the nature and advantages of the present invention maybe realized by reference to the latter portions of the specification andattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following diagrams are merely examples, which should not undulylimit the scope of the claims herein. One of ordinary skill in the artwould recognize many other variations, modifications, and alternatives.It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this process andscope of the appended claims.

FIG. 1 is a simplified block diagram of an integrated optical-electricalsub-module according to an embodiment of the present invention.

FIG. 2 is an exemplary diagram of an optical-electrical transceiverintegrating 4 lasers providing 4 CWDM channels plus 4 replicate channelsaccording to an embodiment of the present invention.

FIG. 3 is a schematic top view of wafer level assembly of a plurality ofin-packaged silicon photonics chips on a single substrate according toan embodiment of the present invention.

FIG. 4 is a schematic top view of an in-packaged optical-electricalmodule of four sub-module light engines according to an embodiment ofthe present invention.

FIG. 5 is an exploded view of a package for the optical-electricalmodule of FIG. 4 integrated with a heatsink and interfaced to a linecard printed circuit board according to an embodiment of the presentinvention.

FIG. 6 is an exploded view of a sub-assembly of four sub-module lightengines in the package of FIG. 5 according to an embodiment of thepresent invention.

FIG. 7 is an exploded view of a sub-assembly of one sub-module lightengine in the sub-assembly of FIG. 6 according to an embodiment of thepresent invention.

FIG. 8 shows an evolution of a light engine chiplet with improved chipdata capacity and reduced lateral dimension according to an embodimentof the present invention.

FIG. 9 is an exploded view of a sub-assembly of a light engine chipletwith reduced lateral dimension according to an embodiment of the presentinvention.

FIG. 10 is a cross-section view of the light engine chiplet of FIG. 9clamped in a socket base and a perspective view of it configured tocouple with an external PLC block integrated in an optical connectoraccording to an embodiment of the present invention.

FIG. 11 is a perspective view of a switch module with a processorco-packaged with multiple light engines commonly on a switch substratefor extra short reach in data communication according to an embodimentof the present invention.

FIG. 12 is a schematic top view of the switch module of the FIG. 11 witha capacity of 51.2 Tbit/s on a switch substrate integrating eight lightengine chiplets per each peripheral side of the switch substrateaccording to the embodiment of the present invention.

FIG. 13 is a schematic diagram illustrating evolved integration schemesof moving light engines closer to a switch processor for reducinginterconnect reach distance in high-speed data communicationapplications according to some embodiments of the present invention.

FIG. 14 is an exploded view of all parts of a package of a light enginechiplet to illustrate a method of packaging one of the multiple lightengines in the co-packaged switch module according to an embodiment ofthe present invention.

FIG. 15 is (A) a perspective view and (B) a side view of the packagedlight engine chiplet of FIG. 14 according to an embodiment of thepresent invention.

FIGS. 16A-16C show a method of releasing a sub-assembly from thepackaged light engine chiplet of FIG. 15 according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to optical telecommunication techniques.More particularly, the present invention provides an in-packagedoptical-electrical module assembling multiple sub-modules on a singleline card, each being configured as a multi-channel light enginecontaining an optical-electrical transceiver based on silicon-photonicsplatform. Merely by example, the present invention discloses asub-assembly for the sub-module integrating 4 laser chips providing 4CWDM channels plus 4 optional replicated CWDM channels on a singlesilicon photonics substrate, a compact package for multiple suchsub-assemblies of sub-modules on a single line card providing 0.4 Tbit/sor higher per sub-module for building desired switching capacity invarious applications of high-speed data communication with differentinterconnect lengths, though other applications are possible.

The following description is presented to enable one of ordinary skillin the art to make and use the invention and to incorporate it in thecontext of particular applications. Various modifications, as well as avariety of uses in different applications will be readily apparent tothose skilled in the art, and the general principles defined herein maybe applied to a wide range of embodiments. Thus, the present inventionis not intended to be limited to the embodiments presented, but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

In the following detailed description, numerous specific details are setforth in order to provide a more thorough understanding of the presentinvention. However, it will be apparent to one skilled in the art thatthe present invention may be practiced without necessarily being limitedto these specific details. In other instances, well-known structures anddevices are shown in block diagram form, rather than in detail, in orderto avoid obscuring the present invention.

The reader's attention is directed to all papers and documents which arefiled concurrently with this specification and which are open to publicinspection with this specification, and the contents of all such papersand documents are incorporated herein by reference. All the featuresdisclosed in this specification, (including any accompanying claims,abstract, and drawings) may be replaced by alternative features servingthe same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

Furthermore, any element in a claim that does not explicitly state“means for” performing a specified function, or “step for” performing aspecific function, is not to be interpreted as a “means” or “step”clause as specified in 35 U.S.C. Section 112, Paragraph 6. Inparticular, the use of “step of” or “act of” in the Claims herein is notintended to invoke the provisions of 35 U.S.C. 112, Paragraph 6.

Please note, if used, the labels left, right, front, back, top, bottom,forward, reverse, clockwise and counter-clockwise have been used forconvenience purposes only and are not intended to imply any particularfixed direction. Instead, they are used to reflect relative locationsand/or directions between various portions of an object.

In an aspect, the present disclosure provides an integratedoptical-electrical sub-module based on silicon photonics platform and anin-packaged optics assembly of four sub-modules on one module substratewith 1.6 Tbit/s or higher optical lane speeds for PAM backplane/opticalreach for various interconnect ranges of data communication. As datatransmission-capacities increase in WDM systems, demand on high-speed,compact optical transceiver based on silicon photonics platformincreasingly attract more and more interest over the recent years. Forexample, a pluggable optical transceiver in compact form factor. Yet,the compact optical transceiver is still a stand-alone device that needsto be coupled with separate passive optical devices like Mux/Demux andone or more gear box or retimer chips to connect with an electricalswitch device to form a functional light engine, which requires a fairlylarge package size and high power-consumption.

FIG. 1 shows a simplified block diagram of an integratedoptical-electrical sub-module according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. As shown, inan embodiment, the integrated optical-electrical sub-module includes anelectrical host interface configured to receive electrical host datainput via N 25G (NRZ) or 50G (PAM4) or 100G (PAM4) channels and adigital processor to process the data signals via retimer chip having Nto N lanes. Optionally, the digital processor processes the data signalvia a gear box N to M lanes where N is a multiple of M. Optionally, theelectrical host interface is configured in one or more chips includingforward error correction (FEC) channel coding for controlling errors indata transmission over unreliable or noisy communication channels. Inthe embodiment, the integrated optical-electrical sub-module alsoincludes an optical line interface configured with 4-wavelength CWDMlasers modulated to convert N electrical data into optical signals in Noptical lanes. Optionally, a light engine with similar configuration canbe formed with >4 wavelengths. Optionally, the 4 or more wavelengths maybe chosen to have half spacing than nominal CWDM channels. The opticalsignals are transmitted via optical line data output multiplexed in awaveguide or optical fiber. Optionally, the laser chips, a Driver chip,and a Transimpedance Amplifier (TIA) chip are integrated on a siliconphotonics substrate. Optionally, the silicon photonics substrate ismounted via an interposer on a same sub-module substrate for mountingthe one or more chips containing the electrical host interface.Optionally, the silicon photonics substrate is the interposer.Optionally, an analog control chip for laser and modulator control ismounted on a backside of the sub-module substrate. Optionally, TIA chipor Driver chip or microcontroller chip can be mounted on the backside ofthe sub-module substrate as well. Optionally, the integratedoptical-electrical sub-module is configured to have an external powerinterface to couple with a power supply and receive module controlsignals via a host control interface such as I2C interface.

FIG. 2 is an exemplary diagram of an optical-electrical transceiverintegrating 4 lasers providing 4 CWDM channels plus 4 replicate channelsaccording to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. In an embodiment, theoptical-electrical transceiver 1000 integrates four laser chips 110 witha driver chip 150 and a TIA chip 140 flip-bonded on a silicon photonics(SiPho) substrate 100 to form a SiPho chip coupled with an externalplanar light circuit (PLC) block 200. As shown, the optical-electricaltransceiver 1000 is specifically configured as a 4-wavelength CWDMoptical transceiver including an optical receive path and an opticaltransmit path. In the optical receive path, it is configured to receiveincoming four light signals with four wavelengths demultiplexed from oneoptical input 221. In the optical transmit path, it is configured tooutput four light signals with four CWDM channel wavelengths multiplexedto one optical output 211. A 4-to-1 multiplexer (Mux) 210 is a PLCwaveguide device formed on a glass or sapphire substrate and configuredto multiplex the four CWDM channel wavelengths into one waveguide oroptical fiber. A 1-to-4 demultiplexer (Demux) 220 is another PLCwaveguide device formed on the same glass or sapphire substrate andconfigured to demultiplex an incoming optical signal to four multiplexedwavelengths which carry high-speed modulated signals from the network.The optical-electrical transceiver 1000 also includes multiplehigh-speed photodetectors 130 to detect each of the four light signalswith four demultiplexed wavelengths. In the embodiment, both the Mux 210and Demux 220 are integrated in the PLC block 200. Optionally, the PLCblock 200 includes multiple optical waveguides formed in a single glassor sapphire substrate aligned with corresponding waveguides in thesilicon photonics substrate 100.

Referring to FIG. 2, the optical-electrical transceiver 1000 includes abank of 4 CWDM lasers 110 respectively provide 4 light signals withrespective CWDM channel wavelengths centered in 1270 nm, 1290 nm, 1310nm, and 1330 nm. Optionally, each laser device is a DFB laser chip.Optionally, each laser chip 110 is provided as an individual laser chipfabricated separately and flip-mounted on the silicon photonicssubstrate 100. Optionally, each light signal outputted from therespective one laser chip is aligned to a silicon waveguide built in thesilicon photonics substrate 100. Each light signal, through the siliconwaveguide, is firstly coupled into a power splitter 120 and is splitinto two light signals in two separate branches with a split ratiovarying from 5:95 to 50:50. Optionally, one split light signal from aminor split branch of the power splitter 120 is used for monitoring orwavelength locking or feedback control. Optionally, one light signalfrom one major split branch of the power splitter 120 is fed to one offour modulators 160. Optionally, the power splitter is a 50:50 splitter,the light signal is converted to two replicate light signals, basicallydoubling the channel numbers. Each replicate light signal is fed into amodulator. Totally, the optical-electrical transceiver 1000 of FIG. 2shows four modulators 160 respectively for receiving light signals fromfour first branches (01) while four other modulators for the four second(replicate) branches (02) are not explicitly shown. Of course, there canbe many variations in functional setups or optical layouts to handlethese light signals and configure in different manners for differentapplications of the optical-electrical sub-module other than the oneoptical-electrical transceiver including 4 CWDM channels plus 4replicate CWDM channels. For example, optionally, the optical-electricaltransceiver 1000 is provided with a set (>4) of lasers with a smallerchannel spacing than the CWDM channels to provide >4 wavelengths. Thewhole system will then have to operate in the same multi-wavelengthplan.

Optionally, the modulator 160 in any one of first branch 01 isconfigured in a linear waveguide-based Mach-Zehnder modulation scheme.Each modulator 160 includes two waveguide branches with desired phasedelay configured to match with respective one of four wavelengths 1270nm, 1290 nm, 1310 nm, and 1330 nm of the four CWDM channels. Optionally,the four wavelengths can be selected from a group of 1270 nm, 1280 nm,1290 nm, and 1300 nm or a group of 1300 nm, 1310 nm, 1320 nm, and 1330nm with smaller channel spacing. Optionally, each wavelength is selectedfrom a range from 1270 nm to 1330 nm as one CWDM channel to support theoptical signal transmission in high-speed (e.g., 100 Gbit/s or higher)data communication. A Driver module 150 is provided as a separatelyfabricated CMOS or SiGe chip flip-mounted on the same silicon photonicssubstrate 100. Optionally, a redundant or a replicate driver module 150′(not shown in FIG. 2) is also provided as a chip flip-mounted on thesame silicon photonics substrate 100 for driving the other fourmodulators in the replicate split branch (not shown). The driver module150 is configured to drive all the four modulators 160 to modulate thelight signals in the four CWDM channels. Optionally, one 8-channeldriver is able to drive the 4 channels plus 4 replicate channels.Optionally, the driver module 150 employs PAM-N (N is an integer)modulation protocol or NRZ modulation protocol to modulate the lightsignal. For example, the modulators 160 are provided assilicon-waveguide-based Mach-Zehnder interferometer configured toprovide PAM4 modulation though other formats can be employed. Aftermodulation, the four CWDM channels of light signals are guided to the4-to-1 multiplexer (Mux) 210 in the PLC block 200 which outputs amultiplexed light signal through an optical fiber (not shown) to anoutput port 211 of the sub-module 1000. Optionally, there is another4-to-1 Mux (yet not shown) formed in the PLC block 200 for combining theother 4 replicate CWDM channels of light signals to one multiplexedlight signal which is through another fiber (not shown) led to theoutput port 211. Effectively, a combination of the 4 laser chips 110 and4 or 8 modulators 160 driven by the driver module 150 or plus areplicate driver module 150′ forms an integrated 4-ch optical transmitpath plus another 4-ch replicate optical transmit path (not shown inFIG. 2).

Referring to FIG. 2 again, the optical-electrical transceiver sub-module1000 includes a 4-ch optical receive path. In the optical receive path,the optical de-multiplexer (Demux) 220 in the PLC block 200 receives anincoming light signal via an input port 221 from an external networkwhich is configured to operate under the four CWDM channel wavelengthsfor transmitting corresponding data signals. The incoming light signalcarrying four multiplexed wavelengths is demultiplexed into 4 separatelight signals in the respective 4 wavelengths guided into respectivefour waveguides formed in the silicon photonics substrate 100. TheHigh-speed photodetectors 130 are used to detect these four lightsignals separately and converted to respective electrical currentsignals. In the embodiment, the 4-channel optical receive path of theoptical -electrical transceiver sub-module 1000 also includes atrans-impedance amplifier (TIA) module 140 for independently processingthe electrical current signals converted from respective four separatelight signals for communicating with host electrical network system viaan electrical host interface. Optionally, the TIA module 140 isseparately formed and flip-mounted on the same silicon photonicssubstrate 100. Optionally, the optical-electrical transceiver sub-module1000 also includes a replicate 4-ch optical receive path as the fourreplicate channel light signals can be demultiplexed from anotherincoming light by another demultiplexer. In the replicate 4-ch opticalreceive path, a replicate TIA module 140′ (not shown) can be includedfor independently processing four more electrical signals converted fromrespective four replicate light signals for communicating with hostelectrical network system with 2× expanded bandwidth. Optionally, theTIA module 140′ is also a flip chip mounted on the same siliconphotonics substrate.

In another aspect, the present disclosure provides a fabrication processfor the integrated optical-electrical sub-module based on siliconphotonics platform such as the transceiver sub-module 1000. In someembodiments, the fabrication process includes wafer level assembly of2.5D silicon photonics substrate involving 2.5D silicon interposer and220 nm silicon-on-insulator (SOI) substrate. The process includesmonolithic formation of multiple silicon or silicon nitride waveguidesin the silicon photonics substrate 100 for connecting or aligning withseveral different silicon photonics devices including power splitters,SiGe or Ge high-speed photodetectors, and Si/SiN-based Mach-Zehnderinterferometer modulator devices formed in the same silicon photonicssubstrate 100. The process also includes coupling the silicon waveguideswith passive PLC devices such as optical multiplexers and demultiplexersformed on a glass or sapphire substrate and mounted onto the siliconphotonics substrate as PLC block 200. The process further includesflip-mounting active devices such as laser chips to the siliconphotonics substrate as an in-packaged design and align the laser chipsdirectly to the waveguides in the silicon photonics substrate or PLCdevices in the PLC block. Optionally, some of the silicon photonicscomponents mentioned above are also silicon waveguides themselvesmonolithically formed in a same manufacture process for preparing thesilicon photonics substrate to integrate the optical-electricaltransceiver sub-module 1000.

FIG. 3 shows a schematic top view of a wafer level assembly of aplurality of in-packaged silicon photonics chips on a single substrateaccording to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown, using theintegrated optical-electrical transceiver sub-module as an example, thesilicon photonics substrate 100 is one die fabricated from a CMOScompatible process plus a post CMOS wafer level assembly out of a SOIwafer 10. In an example, each die 100 is used to form anoptical-electrical module by directly processing the SOI wafer to form asilicon photonics through-substrate via (TSV) interposer. More detailsof the fabrication process involving the TSV interposer can be found inU.S. patent application Ser. No. 15/887,758 filed Feb. 2, 2018 andcommonly assigned to Inphi Corp. Santa Clara, Calif. The as-mentionedapplication is incorporated by reference herein for all purposes.Utilizing the silicon photonics TSV interposer several optical orelectrical components for forming the optical-electrical module can bedirectly mounted on. Referring to FIG. 3, the one die 100 in the wafer10 is enlarged out, showing that several electrical and opticalcomponents including two driver chips 150, 150′, two TIA chips 140,140′, two dummy chips 190, and four field effect transistors 145 (toapply bias to the laser chips 110) is flip-mounted on the top side ofthe die in a post CMOS wafer level assembly. Especially, four laserchips 110 are also directly flip-mounted to respective chip sites on thedie and optically aligned with waveguides formed therein as anin-packaged assembly without any wire bonding.

Additionally referring to FIG. 3, multiple redundant dies are arrangedin multiple pairs of rows on the wafer substrate 10. Each die 100includes four CWDM laser chips 110. The wafer substrate 10 also isconfigured to lay out multiple rows of blink probing pads 300 designedfor conducting wafer level burn-in and testing conveniently. Eachprobing pad 300 includes electrodes 310 for easily coupling withexternal tester electrodes to allow proper bias current being applied inseries to a plurality of laser chips on the wafer substrate 10. Moredetails on designing a chip site on the die for mounting a laser chipand performing wafer level burn-in and testing for the laser chip can befound in U.S. patent application Ser. No. 16/800,974, filed Feb. 25,2020, which is commonly assigned to Inphi Corp. Santa Clara, Calif. andincorporated by reference herein for all purposes.

In yet another aspect, the present disclosure provides an in-packagedoptical-electrical module assembling four optical-electrical sub-modulesas mentioned above. FIG. 4 shows a schematic top view of an in-packagedoptical-electrical module of four sub-module light engines according toan embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. In an embodiment shown in FIG. 4, the in-packagedoptical-electrical module 3000 is provided by integrating foursub-modules 2000A, 2000B, 2000C, and 2000D evenly packaged in fourcompact areas on a common component substrate 2001. Optionally, eachsub-module is formed on its own component substrate which is named as asub-module substrate.

Each of the four sub-modules in FIG. 4 is substantially redundant andindependently functioned as a 4-wavelength transceiver driven by 4in-packaged lasers to provide 4 light signals for 4 CWDM channels plus 4replicate CWDM channels as shown in a block diagram of FIG. 2.Optionally, the in-packaged optical-electrical module can integrate twosub-modules. Optionally, the in-packaged optical-electrical module canintegrate 6 sub-modules or more. Referring to FIG. 4, in an example,each 4-wavelength transceiver includes a silicon-photonics (SiPho) chip100 diced from one die from the wafer substrate 10 of FIG. 3. The fourCWDM channels are provided by four light signals at respective four CWDMchannel wavelengths centered at, 1270 nm, 1290 nm, 1310 nm, and 1330 nmfrom respective 4 laser chips 110 that are directly flip-mounted on theSiPho chip 100 with its p-side facing toward the SiPho chip. The laserlight emitted from each laser chip 110 is aligned to a Si-basedwaveguide formed in the SiPho chip 100. Optionally, the Si-basedwaveguide includes an optical splitter to split the laser light to twobranches to provide 4 CWDM channels and 4 replicate CWDM channels.Correspondingly, on each SiPho Chip 100, one driver chip 150 and one TIAchip 140 are included for handling transmission and detection of lightsignals involving the 4 CWDM channels and one replicate driver chip 150′and one replicate TIA chip 140′ are included for handling transmissionand detection of light signals associated with the 4 replicate CWDMchannels. The SiPho chip 100 is coupled to a planar light circuit (PLC)block 200, both being bonded to a top side of the correspondingsub-module substrate 2001.

Optionally, each of the four sub-modules in FIG. 4, e.g., 2000A in upperleft portion, also includes a digital signal processing (DSP) chip 2030plus an replicate one DSP chip 2030′ and a microcontroller chip 2040,all mounted on the same top side of the sub-module substrate 2001 as theSiPho chip 100 and PLC block 200. Both the driver chip 150 and thedriver chip 150′ are interfaced via an electrical host interface withexternal electrical host system respectively through the digital signalprocessing (DSP) chips 2030 (and 2030′) to handle the electrical datainput from an electrical host. The DSP chips also are configured tointeract via a host control interface with the microcontroller chip 2040to provide module control and power supply required for operating theSiPho chip 100. Optionally, the DSP chips 2030 and 2030′ include a gearbox or retimer chip for converting analog signals to digital signalsthrough N to N lanes electrical data transfer, a digital processor forprocessing the digital signals, one or more interface devices forcommunicating with external electrical host, and current drivers fordriving the four laser chips. Optionally, the microcontroller chip 2040is associated with a respective one sub-module 2000A and is configuredto control operations of the DSP chips 2030, drivers 150, TIA 140, andinterfaces therein. Optionally, the modulators in the SiPho chip 100 areconfigured to modulate the laser light signals based on PAM-N protocol,for example, PAM-4 protocol, or based on NRZ protocol. Optionally, themodulators are configured in a Mach-Zehnder Interferometer formed withSi-based waveguides in the silicon photonics substrate.

The PLC block 200 associated with each of the four sub-modules 2000A(through 2000D) includes at least a first optical multiplexer (see FIG.2) in an optical transmit path to multiplex the four light signals ofthe four CWDM channels into one output light in one optical fiber and asecond optical multiplexer in a replicate optical transmit path tomultiplex the four replicated light signals into another output light inanother optical fiber. Each optical multiplexer in the PLC block 200 isa planar waveguide formed on a glass or sapphire substrate and properlycoupled to one optical fiber. Both optical fibers can be packaged intoone on-board fiber cable 2010A (through 2010D) coupled between the PLCblock 200. For each sub-module, e.g., 2000A, one optical transceivertransmits eight total output light signals carrying 4 CWDM channels plus4 replicate CWDM channels to external optical network. In theembodiment, the compact in-packaged optical-electrical module 3000totally includes four sub-modules 2000A through 2000D, delivering total32 CWDM channel signals to the external optical network.

In the embodiment, the PLC block 200 associated with the same one of thefour sub-modules, e.g., 2000A (through 2000D), also includes a built-inoptical receive path configured to receive incoming light signals viaoptical fibers from network. The PLC block 200 includes at least a firstoptical demultiplexer to demultiplex an incoming light signal from onefiber (carrying 4 wavelengths) to four individual light signals with therespective four CWDM channel wavelengths. Each optical demultiplexer inthe PLC block 200 is a planar waveguide formed on a glass or sapphiresubstrate properly coupled to one optical fiber. Each of the fourindividual light signals is coupled from planar waveguide in the PLCblock 200 to the waveguides in the silicon photonics substrate anddelivered to a photodetector block (referred to FIG. 2). Thephotodetector block (130 as shown in FIG. 2) individually detects andconverts each light signal to an electrical current signal passed to andprocessed by a trans-impedance amplifier (TIA) module 140 to generate avoltage signal. The voltage signal is further handled or digitized andprocessed by on-board DSP chip 2030 and fed to an external electricalhost receiver. The incoming light signal as mentioned above can bereceived via an optical fiber that also is packaged into the on-boardfiber cable 2010A. Optionally, a second optical demultiplexer isincluded in the PLC block 200 for receiving and demultiplexing anotherincoming light signal carrying 4 replicate CWDM channel wavelengths intoa replicate receive optical path to provide additional bandwidth with 4replicate CWDM channels which can be separately detected byphotodetectors and converted to corresponding electrical signals. Theelectrical signals can be processed by a replicated TIA module 140′ anddigitally processed by DSP chip 2030′ in the same sub-module.

In this embodiment, PLC block 200 contains two 4-to-1 multiplexer andtwo 1-to-4 demultiplexer to create two sets of four light paths. For themulti-channel light engine 3000 that packages total fouroptical-electrical sub-modules 2000A, 2000B, 2000C, 2000D, it can detectdifferent input light signals in 32 channels. In a case that eachchannel carries data in a rate of 50 Gbit/s, each quadrant sub-moduledelivers 400 Gbit/s in data rate with 4 CWDM lasers. The in-packagedoptical-electrical module 3000 can provide 1.6 Tbit/s data switchingcommunication capacity. In another case with improved modulators, driverchip, TIA chip, and DSP chip, each channel can carry 100 Gbit/s speedeven though each quadrant sub-module uses the same 4 CWDM lasers. As aresult, the in-packaged optical-electrical module 3000 can expand itsdata switching communication speed up to 3.2 Tbit/s.

In still another aspect, the present disclosure provides a packagingassembly of the in-packaged optical-electrical module of FIG. 4 asmentioned above. The packaging assembly are illustrated with severalexploded views in FIGS. 5, 6, and 7 in different levels of revelation ofthe packaging structures and mounting fixtures for sub-modules andcomponents therein. FIG. 5 is an exploded view of a packaging assembly5000 of the in-packaged optical-electrical module of FIG. 4 integratedwith a heatsink and interfaced to a module line card based on a printedcircuit board according to an embodiment of the present invention. FIG.6 shows a sub-assembly 3000A for packing four sub-modules within thepackaging assembly of the four sub-modules in FIG. 5 according to anembodiment of the present invention. FIG. 7 shows a detailedsub-assembly 2000A of all components in one sub-module in FIG. 5 andFIG. 6 according to an embodiment of the present invention. Thesediagrams are merely examples, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications.

As shown in FIG. 5, the packaging assembly 5000 is provided bycompressing a sub-assembly 3000A of the multi-channel light engine 3000of FIG. 4 between a top plate member 3020 on top and a backplate member3060 at bottom. The sub-assembly 3000A of the in-packagedoptical-electrical module 3000, as shown in FIG. 6, includes a singlepiece of solid frame fixture member 3002 having two crossly-linkedmiddle bars to form four closely packed window structures, 3008A, 3008B,3008C, and 3008D. The four window structures are designed to allowrespective four sub-assemblies, i.e., 2000A, 2000B, 2000C, and 2000D tofit in. Each sub-assembly (e.g., 2000A) is designed to have thecorresponding sub-module packaged within a case enclosed by a lid member2200A on top sealed with a peripheral side member 2100A around aperipheral region of a sub-module substrate 2300A at bottom. FIG. 7shows package structures and component layouts within each sub-assemblyof a sub-module (e.g., 2000A). More details will be described infollowing paragraphs.

Referring to FIG. 6, the solid fixture member 3002 includes notches3005-1 and 3005-2 at least partially opened downward at one middle barand one side of the frame fixture member 3002. The lid member (e.g.,2200B) of each sub-assembly (e.g., 2000B) includes an open slot 2105-Bfacing upward through a length of one side of the peripheral side member2100B to align with the notch 3005-1. The open slot 2105-B provides anopen space for laying a pair of fiber cables 2010AB which respectivelypackages optical fibers out of the optical-electrical sub-module in thesub-assembly 2000A and 2000B. Similarly, another pair of fiber cables2010CD also packages optical fibers out of the sub-assembly 2000D andsub-assembly 2000C and is laid in the open space provided by the openslot 2105-C aligned with the notch 3005-2.

Referring to FIG. 5 and FIG. 6, as the sub-assembly 3000A is assembledin the packaging assembly 5000, top surfaces of the lid members (e.g.,2200A) of four sub-assemblies (e.g., 2000A) are mechanically pressed ina good thermal contact against a bottom surface of the top plate member3020 in the packaging assembly 5000. In an embodiment, as shown in FIG.5, a top side of the top plate member 3020 is configured with a heatsinkhaving a plurality of fin structures 3021 extended vertically. Theheight of the plurality of fin structures are designed to help releasemodule heat with a sufficiently high efficiency. Optionally, a thermalpad (not shown) can be inserted between the top surface of the lidmembers and the bottom surface of the top plate member 3020 to enhancethe thermal conductivity. The heatsink is configured to release the heatgenerated by the four sub-modules in the sub-assembly 3000A in whicheach sub-module contains 4 CWDM lasers and multiple pre-packaged CMOSchips like the driver chip 150 and TIA chip 140 and DSP chip 2030.Mechanically, the top plate member 3020 is pressed by severalspring-loaded compression pins 3030 with threaded head applied from thetop side to lock in respective sockets 3063 with the backplate member3060 in the package assembly 5000.

Referring to FIG. 7, the sub-assembly of the sub-module 2000A includes acase having a top lid member 2200A covering a peripheral side member2100A located around a peripheral boundary region on top of a sub-modulesubstrate 2300A which is served as a bottom member for the sub-assembly2000A. Optionally, the sub-assembly 2000A is a quadrant portion fittedin one of four window structures (e.g., 3008A) of the packagesub-assembly 3000A. Optionally, the peripheral side member 2100Aincludes at least an open slot 2105-A for laying at least a fiber cable2010A for optical input/output fibers of the optical-electricalsub-module in the sub-assembly. Optionally, a top surface 2201A of thelid member 2200A may be attached with a thermal pad (not shown) forenhancing heat release efficiency of the sub-assembly 2000A. Optionally,the sub-module substrate 2300A also is structured to allow heat beingconducted effectively through itself.

In one embodiment, as illustrated in FIG. 7, the sub-module packaged inthe sub-assembly 2000A includes a SiPho chip packaged on asilicon-photonics substrate 100 which is mounted on a top side of thesub-module substrate 2001A. The SiPho chip 100 is substantially the sameas one die formed on a SOI wafer 10 using wafer level assembly processas shown in FIG. 3. Referring to FIG. 7, the SiPho chip 100 includes adriver chip 150 and a replicate driver chip 150′, a TIA chip 140 and areplicate TIA chip 140′, and four laser chips 110, all flip-mounted ontop of the same silicon-photonics substrate 100. Some dummy chips (notshown) and field-effect transistor devices 145 can also mounted on topof the same silicon-photonics substrate 100. The SiPho chip includes atransmitter unit configured to generate multi-channel optical signalsfrom the four laser chips which are modulated by four modulator devicesdriven by the driver chip based on data received via an electricalinterface block. The multi-channel optical signals are transmitted to anoptical transmit path coupled to an optical interface block to output amultiplexed optical signal.

In the embodiment, the same SiPho chip also includes a receiver unitconfigured to use a set of photodetectors to detect multi-channeloptical signals received in an optical receive path and demultiplexed inthe optical interface block from an incoming multiplexed optical signaland use the TIA chip to convert the detected multi-channel opticalsignals to current signals which are digitized and processed in theelectrical interface block before being delivered as N to N lanes ofdigitized signals for electrical host including an optical transmit pathand an optical receive path in the same silicon photonics substrate 100.One driver chip 150 and one TIA chip 140 in the SiPho chip are involvedin handling transmission of four light signals from the four laser chipsto the optical transmit path and detecting four incoming light signalsfrom the optical receive path. Another driver chip 150′ and another TIAchip 140′ are separately involved in handling transmission of fourreplicate light signals from the four laser chips to the opticaltransmit path and detecting four additional incoming light signals fromthe optical receive path. These TIA/Driver chips in each SiPho chip ofthe packaged sub-assembly 2000A are configured to handle reception andtransmission of light signals in two replicate sets of 4 CWDM channelswith respective wavelengths centered at 1270 nm, 1290 nm, 1310 nm, and1330 nm. Optionally, the electrical interface block comprises a digitalsignal processing (DSP) chip 2030 configured to process N to N Lanes ofdigitized signals with a data rate of 25 Gbit/s per lane. Optionally,the electrical interface block comprises a digital signal processing(DSP) chip 2030 configured to process N to N Lanes of digitized signalswith a data rate of 50 Gbit/s per lane. Optionally, the electricalinterface block comprises a digital signal processing (DSP) chip 2030configured to process N to N Lanes of digitized signals with a data rateof 50 Gbit/s per lane. Optionally, the electrical interface blockcomprises a replicate digital signal processing (DSP) chip 2030′ and amicrocontroller chip 2040.

Additionally referring to FIG. 7, disposed along one side of the SiPhochip on the silicon photonics substrate 100, a PLC block 200 is alsomounted on the sub-module substrate 2300A. The PLC block 200 includesone or more multiplexers and demultiplexers in PLC-based waveguideformed on a glass or sapphire substrate for guiding light waves to anoptical output port and from an optical input port of the sub-assembly2000A by coupling light signals between the PLC block 200 andinput/output optical fibers. The input/output optical fibers per onesub-assembly are packaged in one fiber cable 2005-1.

Furthermore referring to FIG. 7, disposed along another side of theSiPho chip on the silicon photonics substrate 100, one or more ASICchips, for example, digital signal processing (DSP) chip(s) 2030(2030′),can be flip-mounted on the same sub-module substrate 2300A. Each DSPchip 2030 or 2030′ is configured in an electrical interface block tosupport functions of one TIA chip 140 and one driver chip 150 forprocessing or modulating optical/electrical signals involving a 4-chCWDM optical transmit/receive path or one replicate TIA chip 140′ andone replicate driver chip 150′ for processing or modulatingoptical/electrical signals involving a replicate 4-ch CWDMtransmit/receive path. Moreover, a microcontroller chip 2040 is alsoflip-mounted to the sub-module substrate 2300A next to the replicate DSPchip 2030′ and configured in the electrical interface block to supportoperation of the DSP chip or replicate DSP chip as well as the operationof SiPho chip. Referring to FIG. 7, the DSP chips 2030 (2030′), ormicrocontroller chip 2040 are mounted onto a front side of thesub-module substrate 2300A via multiple conductive bonding bumps 2108.Optionally, the sub-module substrate 2300A also provides its bottom sidefor mounting additional functional chips for utilizing the substratemore efficiently to enhance performance of the light engine. Forexample, an ASIC chip 2050 for analog controls for the laser andmodulator is mounted at the bottom side of the sub-module substrate2300A via multiple bumps 2109 based on through-substrate vias.

Referring to FIG. 5 and FIG. 6, the sub-assembly 3000A of thein-packaged light engine 3000 is received by or disposed in a socketframe member 3010 from its top side. An interposer plate 3040 isconfigured to be disposed between bottom side of the four sub-modulesubstrates (e.g., 2300A) of the sub-assembly 3000A and a top side of amodule substrate 3050. Optionally, the four sub-module substrates 2300Athrough 2300D (see FIG. 6) may be considered as one common substrate.Optionally, the module substrate 3050 is configured to serve as a linecard including relevant electrical connection circuits in a printedcircuit board (PCB) to the host. Optionally, the module substrate 3050is a part of a larger line card by itself. The PCB associated with themodule substrate 3050 is configured with integrated circuits with a lineinterface connecting via the four sets of conducting bump contacts tothe four sub-assemblies of the optical-electrical sub-modules andconfigured as a line card with a host interface for connecting themulti-channel light engine to a data center and with an external powerinterface for accessing external power supply. Optionally, theinterposer plate 3040 includes four groups of patternedthrough-substrate-vias (TSVs) (e.g., 3044A) designed for coupling thebottom sides of four sub-module substrates 2300A through 2300Drespectively for the four optical-electrical sub-modules 2000A through2000D.

Optionally, the interposer plate 3040 is a passive interposer providedwith four quadrant grids of conductor-filled through-substrate via(TSVs) bumps respectively formed on four quadrant regions of theinterposer plate projected to the four sub-module substrates. Forexample, the quadrant grid of TSV bumps 3044A is designed for formingelectrical connections between the sub-module substrate 2300A to directbonding interconnects (DBI) contacts 3052A in a corresponding quadrantregion of the module substrate 3050. Optionally, each quadrant grid ofTSV bumps (e.g., 3044A) is provided to surround a quadrant hollow region(e.g., 3042A) of the interposer plate 3040 to yield the space foroptional ASIC chip (e.g., 2050 in FIG. 7) mounted on the back side ofthe sub-module substrate (e.g., 2300A).

Optionally, the interposer plate 3040 is an active interposer thatcontains four quadrant grids of TSV bumps to connect lOs and supply aswell as to provide active regions with embedded circuit devices to passelectrical signals using buffers between two DBI contacts. Optionally,the interposer plate 3040 is a 2.5D silicon interposer. Optionally, theinterposer plate 3040 is a 3D silicon interposer.

Referring to FIG. 5, the module substrate 3050 includes severalalignment through-holes 3051 aligned with similar alignmentthrough-holes 3041 in the interposer plate 3040 and that 3011 in thesocket frame member 3010. The backplate member 3060 includes analignment pin 3061 configured to pass through those alignmentthrough-holes 3051, 3041, and 3011 for properly stacking these assemblymembers together. The module substrate 3050 also has severalthrough-holes 3053 allowing the compression pins 3030 to pass forlocking all parts in the package assembly 5000 with the backplate member3060. The backplate member 3060 includes several opened window regions(e.g., 3062A) designed to provide space for mounting additional chips onthe backside of the module substrate 3050. Optionally, these windowregions provide better thermal conductivity for the package assembly5000. The backplate member 3060 has several threaded holes 3063 allowingthe corresponding compression pins 3030 with threaded head to lock inthere so that the package assembly 5000 is tightly assembled.

In still another aspect, the present invention provides a light enginechiplet that integrates a silicon photonics (SiPho) chip withopto-electrical interfaces to form a multi-channel transceiver in acompact package on a single substrate. Optionally, the light enginechiplet is provided as one integrated optical-electrical module outlinedin FIG. 1 to receive data in 25G or 50G or 100G for driving 4-wavelengthlasers to achieve N electrical to N optical lanes communication.Optionally, the light engine chiplet is configured as anoptical-electrical transceiver integrating 4 lasers with a driver moduleand a TIA module on a silicon photonics substrate to provide 4 CWDMchannels plus 4 replicate channels coupled to a PLC block as shown inFIG. 2. Optionally, the light engine chiplet is provided as a quadrantsub-module on a same module substrate of an in-packagedoptical-electrical module 3000 in FIG. 4. Alternatively, the in-packagedoptical-electrical module can assemble two light engine chiplets or sixlight engine chiplets depending on different capacities, reach ranges,and bandwidth requirements for different high-speed data communicationapplications.

FIG. 8 shows an evolution of a light engine chiplet with improved chipdata capacity and reduced lateral dimension according to an embodimentof the present invention. This diagram is merely an example, whichshould not unduly limit the scope of the claims. One of ordinary skillin the art would recognize many variations, alternatives, andmodifications. Referring to part A of the FIG. 8, the light enginechiplet is substantially the same as an optical-electrical sub-module2000A disposed as a quadrant of the in-packaged optical-electricalmodule 3000 shown in FIG. 4. As described in FIG. 4, the light enginechiplet 2000A includes a SiPho chip 100 which integrates four laserchips 110 with a driver chip 150 and a TIA chip 140 as well as areplicate driver chip 150′ and a replicate TIA chip 140′ all mounted ona silicon photonics substrate and together functioned as a multi-channeloptical-electrical transceiver. The SiPho chip 100 is mounted on asub-module substrate shared with a DSP chip 2030 and a microcontrollerchip 2040 as well as a replicate DSP chip 2030′ and a PLC block 200. Inthe silicon photonics substrate, several waveguide-based 1-to-2 opticalsplitters are built in to split each laser light from a respective oneof the four laser chips 110 into two branches, providing 4 replicatechannels for respective 4 CWDM channels with center wavelengths at 1270nm, 1290 nm, 1310 nm, and 1330 nm, respectively. Depending on the DSPchips and microcontroller chip and associated electrical host data inputand host interface setting, a data rate per channel can be provided with25G using NRZ modulation protocol to modulate each of the four lasers110, yielding 25G×8=0.2 Tbit/s per light engine. If a data rate perchannel is given by 50G using PAM-4 modulation protocol to modulate eachlaser, it gives 0.4 Tbit/s per light engine with 8 optical lanes.Optionally, the light engine chiplet 2000A can be provided as oneindependent unit assembled within a four-unit optical-electrical module3000 as shown in FIG. 4.

Referring to part B of the FIG. 8, the light engine chiplet 4000A isstill a multi-channel transceiver configured with a substantially samesetting as the light engine chiplet 2000A in chip layout, chip size,laser driving, silicon photonics substrate and waveguide design, andsub-module substrate design. The improvement lies in upgradation ofcorresponding chips and laser modulation scheme therein. For example,DSP chip 4030, 4030′, microcontroller chip 4040, driver chip 300, TIAchip 280, replicate driver chip 300′ and replicate TIA chip 280′, andhost data rate loaded via electrical host interface are upgraded to 100Gper channel using PAM-4 modulation protocol with a rate of 56Gbaud/λ sothat the data capacity per light engine chiplet is doubled to 0.8Tbit/s. The PLC block 200 and laser chips 110 can be substantially nochange versus those in the light engine chiplet 2000A. Optionally, thelight engine chiplet 4000A can be a quadrant of four-sub-module assemblyindependently operated in an optical-electrical module. Optionally, thelight engine chiplet 4000A can be provided as one independent unitassembled within a multi-unit optical-electrical module.

Referring to part C of the FIG. 8, in an embodiment, the light enginechiplet 8000 is reconfigured to reduce the package size substantially.An integrated CMOS chip 4340 and a newly designed SiPho chip are mountedon a smaller sub-module substrate in a reduced lateral dimension.Optionally, the light engine chiplet 8000 are provided in a lateraldimension of 10 mm×10 mm or less, substantially reduced from 25 mm×25 mmfor the light engine chiplet 2000A or 4000A. In the embodiment, anintegrated processing chip 4340 combines the DSP chip (e.g., 4030) withthe microcontroller chip (e.g., 4040) to provide electrical hostinterface for the multi-channel transceiver. Additionally, the driverchip(s) are alternatively integrated into the CMOS circuit (not visiblein the figure). The TIA chip(s) 480 (480′) have reduced sizes and aremounted on the newly designed SiPho chip on silicon photonics substrate100′.

Optionally, the SiPho chip of the light engine chiplet 8000 stillintegrates 4 laser chips 110′ on the silicon photonics substrate 100′.But all laser chips are redesigned for emitting laser light with higherpower. In the silicon photonics substrate 100′, several waveguide-based1-to-4 optical splitters can be formed to yield 4 replicate channels perone laser. Thus, each light engine chiplet 8000 can provides 16 channelsor 4 sets of 4 CWDM channels to yield total 1.6 Tbit/s capacity if eachchannel is provided with 100 Gbit/s capacity under PAM-4 56Gbaud datamodulation. Optionally, the high-power laser chips could be mounted onthe silicon photonics substrate 100′, or mounted externally and coupledinto the waveguide-based devices in the silicon photonics substrate100′. Optionally, the SiPho chip of the light engine chiplet 8000 canintegrate 8 laser chips when each laser chip is coupled to a 1-to-2optical splitter. Optionally, the light engine chiplet 8000 still justintegrate 4 laser chips 110′ on the silicon photonics substrate 100′respectively coupled to four 1-to-2 optical splitters, giving 8 channelsper chiplet. Optionally, a next generation modulation scheme using PAM-6or PAM-8, or using higher Gbaud rate under PAM-4, a 200 Gbit/s perwavelength capacity can be provided so that each light engine chiplet ina 10 mm×10 mm package can still yield 1.6 Tbit/s capacity. Optionally,coherent polarized light signal can be implemented to provide directly200 Gbit/s or 400G it/s per wavelength in bandwidth to allow eachchiplet to support extra-high data rate communication. Optionally, thelight engine chiplet 8000 can be provided as one independent unitassembled within a multi-unit optical-electrical module or directlyintegrated on a same switch substrate with multiple chiplets and aswitch processor.

Referring to part C of FIG. 8, the smaller sub-module substrate of thelight engine chiplet 8000 forces some changes in the packaging assemblyof all optical-electrical components therein. For example, the lateraldimension of the chiplet 8000 can be reduced to 10 mm×10 mm or smaller.FIG. 9 is an exploded view of a sub-assembly of a light engine chipletwith reduced lateral dimension according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. Referring toFIG. 9, the packaging assembly 8000A of the light engine chipletincludes a vertical stacking assembly of multiple chips on separatecomponent substrates unlike the light engine chiplet 2000A for keepingthe CMOS chips, SiPho chip, and PLC block on a single sub-modulesubstrate 2300A (see FIG. 8). As an example, the packaging assembly8000A includes a lid member 8100 configured with a top plate 8101connected to four side walls 8105. At least one side wall 8105 includesan opening port 8110 configured to allow an optical connector (see FIG.10 below) to plug in. The lid member 8100 also includes an opticalconnector interface structure (not visible) under the top plate 8101coupled to the open port 8110 to allow at least one optical output andone optical input to be aligned with the respective pathways of theoptical connector. Optionally, the optical connector interface is aparallel fiber interface. Optionally, the lid member 8100 is also madeas a heat sink. Optionally, the top plate 8101 can be made by ahigh-thermal-conductivity material to serve as the heat sink forefficiently transfer heat out of the packaging assembly 8000A.Optionally, additional thermal conductive structure is fabricated on topof the top plate 8101 to serve as a heat sink that fit in varioussystems such as optical switch module with co-packaged light engines ina rack chassis.

Referring to FIG. 9, the light engine chiplet in the packaging assembly8000A includes a first component substrate 8200 integrating anapplication-specific integrated circuit (ASIC) chip including a digitalsignal processing (DSP) chip, optionally a microcontroller chip, andhost/line interface IC in a CMOS platform (e.g., 5 nm process). The DSPchip is at least configured to serve as a digital signal processinginterface of the light engine functioned as an optical-electricaltransceiver. A host interface integrated in the first componentsubstrate 8200 is configured to perform data interconnect operation withan extra-short reach (XSR) or equivalent protocol to interact withsystem processor or electrical host. A line interface integrated in thefirst component substrate 8200 is configured to support PAM opticalreach (POR) control of the light engine operation. Optionally, the DSPchip also includes Physical Code Sublayer (PCS) or Physical MediumAttachment (PMA) layers for data encoding and decoding or many otherdigital signal processing operations. Optionally, the first componentsubstrate 8200 is disposed as a top die of the stack-up componentsubstrates (dies) at a nearest position under the lid member 8100.Optionally, the first component substrate 8200 also integrates modulatordriver and microcontroller directly into the DSP chip. Optionally, theDSP function in the ASIC chip is incorporated to a system processor andthe first component substrate 8200 only retains integrated modulatordriver and transimpedance amplifier function. Optionally, the ASIC chipincludes SerDes chip for coding and encoding data through the DSPinterface.

Referring to FIG. 9, the light engine chiplet in the packaging assembly8000A includes a second component substrate 8300 integrating anapplication-specific integrated circuit (ASIC) control chip and a thirdcomponent substrate 8400 integrating a TIA chip, both being disposedbelow the first component substrate 8200. Optionally, the TIA chip iscoupled to bottom conductive contacts of the first component substrate8200 via a set of bumps 8410 on the third component substrate 8400. TheASIC control chip is configured to couple to bottom of the firstcomponent substrate 8200 via another set of bumps 8310 on the secondcomponent substrate 8300. The second component substrate 8300 and thethird component substrate 8400 (or maybe a combined substrate) thus aredisposed as a middle die under the top die of the stack-up componentsubstrates in the packaged assembly 8000A. Optionally, the TIA chip isreduced in size and mounted or integrated into a silicon photonics(SiPho) chip below and the ASIC control chip in the second componentsubstrate 8300 may be integrated into the DSP chip in the top die in thefirst component substrate 8200. Optionally, the TIA chip may be alsointegrated into the DSP chip in the top die associated with the firstcomponent substrate 8200. In this case, the middle die of the stack-upcan be eliminated.

Referring to FIG. 9, the light engine chiplet in the packaging assembly8000A includes a fourth component substrate 8500 made by a siliconphotonics substrate integrating various Si or SiGe-based waveguidedevices such as optical modulators and photodetectors. Optionally, thefourth component substrate 8500 by itself forms a SiPho chip as anindividual die in the stack-up. Optionally, the SiPho chip is coupledvia a set of bumps 8510 to the ASIC control chip in the second componentsubstrate 8300 for controlling the operation of DSP chip or TIA chip.The SiPho chip is also coupled via a set of bumps 8512 to the TIA chipin the third component substrate 8400 for passing the incoming opticalsignals to the photodetectors which generate photocurrent signals forthe TIA chip. Optionally, the SiPho chip in the fourth componentsubstrate 8500 also directly integrates multiple, e.g., four, laserchips as light sources to provide multiple optical channels of theoptical-electrical transceiver for optical data communication, adesignated function of the light engine chiplet. Optionally, the laserchips, especially, high-powered laser chips can be disposed outside thepackaging assembly 8000A. Optionally, the fourth component substrate8500 is disposed as a bottom die under the middle die more distal to thetop die in the stack-up in the packaging assembly 8000A. Optionally, asthe middle die is partially absorbed into either the top die or bottomdie, for example, the ASIC control chip is incorporated into the DSPchip and the TIA chip is reduced in size and mounted or embedded intothe SiPho chip, the bottom die associated with the fourth componentsubstrate 8500 may be directly coupled with the top die associated withthe first component substrate 8200. Alternatively, the first componentsubstrate 8200 is disposed as a bottom die while the fourth componentsubstrate 8500 can be disposed as a top die in the stack-up in thepackaging assembly 8000A.

Referring to FIG. 9, the light engine chiplet in the packaging assembly8000A includes a sub-module substrate 8600 served as a bottom member ofthe packaged assembly 8000A. The sub-module substrate 8600 is providedas a micro land grid array (LGA) substrate which includes a matrix arrayof conductive socket contacts 8610 convenient for chip testing andsurface-mount packaging assembly. Optionally, the micro-LGA substrate isalso designated for mounting the light engine chiplet onto a modulesubstrate by connecting the conductive socket contacts to a printedcircuit board line card designed for being used in an optical networksystem in a rack chassis. Optionally, the sub-module substrate 8600 is a2.5D substrate having through-vias to connect all active componentswithout any wire bonding. Optionally, power regulators and decouplingcapacitors may be integrated into ASIC chips such as the digital signalprocessing chip as no power supplies are provided in the micro-LGAsubstrate for the light engine chiplet in this compact packagingassembly 8000A. Optionally, all components in the packaging assembly8000A as described above has a lateral dimension substantially limitedby the sub-module substrate 8600. It is desired to push the lateraldimension smaller and smaller except that high-powered laser may have tobe mounted externally instead of integrated in the SiPho chips therein.In an example, the lateral dimension is as small as 10 mm×10 mm.

Referring to part C of FIG. 8 and FIG. 9, the sub-module substrate 8600for supporting the light engine chiplet 8000 is reduced in sizecomparing to that 2300A for supporting the light engine 2000A or 4000A.In these embodiments, the sub-module substrate, for example, a dimensionof the sub-module substrate is only 10 mm×10 mm. The substrate with sucha small dimension may not have room for mounting a PLC block like onePLC 200 in the light engine chiplet 2000A or 4000A. The PLC blockcontaining at least a multiplexer and a demultiplexer in planar lightcircuit form is served as a key component of an optical line interfacethat needs to be coupled with the SiPho chip in the light engine chipletoperated as a multi-channel optical-electrical transceiver. Unlike thelight engine (2000A or 4000A) packaged on a larger sub-module substrate,FIG. 10 shows, in a perspective view at bottom, that the light enginechiplet of FIG. 9 is configured to couple with an external PLC blockintegrated in an optical connector according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims. One of ordinary skill in the artwould recognize many variations, alternatives, and modifications. In anembodiment, as shown in FIG. 10, a PLC block 8700 is disposed outsidethe packaging assembly 8000A of the light engine chiplet. The PLC block8700 includes at least a multiplexer 8710 and a demultiplexer 8720formed as planar waveguide devices on a glass substrate. One end of thePLC block 8700 is coupled to a coupling head 8910 with two alignmentpins 8915 being plugged into two sockets in the optical port 8110 andallowed several on-board fibers (not shown) to couple with themultiplexer 8710 and a demultiplexer 8720 and with respectiveoutput/input waveguides in the SiPho chip in the light engine chiplet.Another end of the PLC block 8700 is coupled to an optical adaptor 8800which aligns the planar waveguide devices in the PLC block 8700 tocorresponding in/out optical fibers. A fiber cable 8900 is configured topack all in/out optical fibers together and connected to an opticalconnector for connecting to an optical network system.

FIG. 10 also shows, in a cross-section view at top, that the packagingassembly 8000A of the light engine chiplet is clamped in a socket basemember 8010. As shown, under the lid member 8100, a stack-up of multipledies are assembled together including a DSP die plus host interface inthe first component substrate 8200 on the top, controller chip in asecond component substrate 8300 and a TIA chip in the third componentsubstrate 8400 side-by-side in the middle, and a SiPho die in thesilicon photonics substrate 8500 at the bottom on the sub-modulesubstrate 8600 which serves as a bottom member. The socket base member8010 includes several bottom notches 8015 (seen in the perspective view)configured to allow a shaped metal wire 8020 to clamp the packagingassembly 8000A with spring force onto the socket base member 8010. Thesocket base member 8010 also includes alignment pins 8012 (seen in thecross-section view) at the bottom thereof used for disposing the clampedpackaging assembly of the light engine chiplet onto a pre-definedlocation in a module substrate (e.g., a switch substrate). The socketbase member 8010 also includes a plurality of thru-vias configured tohave conductor pins or wires 8018 installed for forming properelectrical connection between the packaging assembly 8000A of the lightengine chiplet and a module processor/controller (not shown) on the samemodule substrate. Optionally, the lateral dimension of the socket basemember 8010 holding the packaged assembly 8000A is substantially 10mm×10 mm.

In still another aspect, the present disclosure provides a co-packagedoptical module with a switch processor and multiple light enginechiplets commonly mounted on a switch substrate for extra short reachinterconnect or equivalent protocol in high-speed data communication.With obvious benefit of reduced interconnect loss (<10 dB) in sight,optics based on silicon photonics platform is brought closer and closerto a switch processor for meeting demands on increasing data rate inhigh-speed data communication. As shown in FIG. 9 and FIG. 10, a lightengine configured as a multi-channel optical-electrical transceiver canbe integrated on a compact sub-module substrate based on 2.5D LGA in achiplet packaging assembly. An external PLC block can be provided in anintegrated optical connector to couple with on-board fibers connected toSiPho chip in the light engine. Optionally, the light engine can usehost FEC to draw control signals without using gear box or retimermodule. Such light engine chiplet packaged as shown in FIG. 8 and FIG. 9can be operated independently as multiple replicable units for providingdesired number of optical signal lines or channels needed forUltra-Short-Reach (USR) or Extra-Short-Reach (XSR) or equivalentprotocol in electrical host interconnect operation via a single switchprocessor to communicate with multiple hosts and lines in one modularsetting.

FIG. 11 is a perspective view of a co-packaged optical module of aswitch processor mounted with multiple light engines commonly on aswitch substrate for extra short reach or equivalent protocol in datacommunication according to an embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As an embodiment shown inFIG. 11, the co-packaged optical (CPO) module 9000 is provided byintegrating one switch processor 9100 with multiple packaged lightengine chiplets 9201 commonly on a switch substrate 9001. In anembodiment, the switch processor 9100 is mounted in a central site ofthe switch substrate 9001 while all the multiple packaged light enginechiplets 9201 are substantially evenly distributed at periphery sites onthe switch substrate 9001 surrounding the switch processor 9100.Optionally, the switch substrate 9001 is in a square shape having fourperipheral sides for mounting equal-number of the packaged light enginechiplets 9201 per side. Each packaged light engine chiplets 9201 issubstantially the same as one packaging assembly 8000A of amulti-channel optical-electrical transceiver provided in FIG. 9 beingclamped in a socket base member 8010 as shown in FIG. 10. Each clampedchiplets is mounted into the switch substrate 9001 by using a couple ofalignment pins (8012, see FIG. 10) at bottom of the socket base member8010.

In a specific embodiment, each packaged light engine chiplets 9201includes an optical connector port for plugging-in an optical connectorhead that is coupled to a PLC block to serve its optical line interfacefor the multi-channel optical-electrical transceiver. Optionally, eachchiplet integrates four laser chips in a silicon photonics substrate toprovide four CWDM wavelengths corresponding to four optical channels ofthe optical-electrical transceiver. Optionally, four 1-to-2 splitterscan be added to split each laser light to two to provide four morereplicate optical channels with the same four CWDM wavelengths.Optionally, each chiplet can integrate four more laser chips or choosefour 1-to-4 splitters for four high-powered laser chips to yield 8 or 16channels. Each light engine chiplet can fully be operated independentlywith its own controller and driver. Thus, in the co-packaged opticsconfiguration as shown in FIG. 11, one switch processor can beco-packaged with some pre-determined numbers of light engine chiplets onthe same switch substrate depending on designed processor with maximumdie size and data handling capacities in one co-packaged switch modulein a rack chassis for different applications. Referring to the exampleshown in FIG. 11, one switch processor 9100 is co-packaged with 8 lightengine chiplets 9201 on each of peripheral sides of a switch substrate9001. If each light engine chiplet has 8 channels with 200 Gbit/s perchannel or 16 channels with 100 Gbit/s per channel, the single packagedchiplet 9201 provides 1.6 Tbit/s capacity and the co-packaged optical(CPO) module 9000 is enabled for 51.2T operation. In an alternativeexample, one switch processor can be co-packaged with one light enginechiplets on each of peripheral sides of the switch substrate for switchand optical interconnect, then the CPO module is enabled for 6.4Toperation. Optionally, a CPO module can be enabled for 25.6T operationby co-packaging one switch processor with four light engine chiplets oneach of peripheral sides of the switch substrate for switch and opticalinterconnect.

In an embodiment, a goal of moving optical-electrical module closer andcloser to the switch processor from using pluggable optical module withgear box or retimer to on-board in-package optics and further to theco-packaged optical module that eliminates the gear box or retimer is toreduce power loss (from 20 to 35 dB down to <10 dB) depended on therange of interconnect and substantially reduce power consumption per bitfrom about 5.0 pJ/bit to <1.8 pJ/bit. Since the switch processor has itsown limits on package size especially when its operation capacity isincreased to 51.2T generation, a requirement for smaller total modulepackage size and push for smaller distance between the switch processorand each light engine co-packaged naturally put limitations on both thesize of switch substrate and the size of light engine (or sub-module)substrate.

FIG. 12 shows a top view of a schematic co-packaged switch moduleco-packaged with 32 packaged light engine chiplets (average 8 chipletsper side) with 1.6T capacity per light engine commonly on a 100 mm×100mm switch substrate. The switch processor has a reticle size of about800 mm² for achieving the 51.2 Tbit/s total throughput in single die tobe compatible with the 32 packaged light engines each independently with1.6 Tbit/s capacity. To fit in the length of 100 mm for every peripheraledge, each packaged light engine chiplet is limited to an area of about10 mm×10 mm. Referring to FIG. 9 and FIG. 10, each light engine chipletis in-packaged with minimum functionality of digital processing/hostinterface with enabled Extra-Short-Reach (XSR) or Physical Code Sublayer(PCS) or Physical Medium Attachment (PMA) layers in the DSP chip toreduce the sub-module substrate to 10 mm×10 mm. Optionally, thedriver/TIA chips also are reduced their footprint in the chiplet with astack-up mounting scheme or are incorporated completely into the DSPchip. Depending which chiplet among each peripheral side of the 100mm×100 mm switch substrate, the maximum distance from the switchprocessor die edge to furthest light engine chiplet is smaller than 50mm. As the result, a most-compact switch module with 51.2Tbit/s totalthroughput based on the 10 mm×10 mm 1.6 Tbit/s light engine is shown inFIG. 11 and FIG. 12. In general, for a given total data throughput of aco-packaged switch module with a configuration of a plurality of chipletdies surrounding a main processor die in the central location, eachchiplet die is preferred to have a minimum die size to allow a maximumnumber of chiplet dies disposed densely on the module substrate with adistance of any chiplet die from the main die as small as possible forextra-short-reach or equivalent protocol in data interconnect operation.Also, each chiplet die is preferred to have higher data capacity so thatsmaller numbers of chiplet dies are needed.

Note, for each 10 mm×10 mm 1.6T light engine, 4 (or even 8) laser chipscan still be integrated inside the chiplet package (FIG. 9 and FIG. 10)to provide 4 (or 8) CWDM wavelengths. While a compactmultiplexer/demultiplexer optical interface is developed to beintegrated into an optical connector that plugs into an optical port ofeach light engine chiplet to save space. As shown in FIG. 11, each lightengine chiplet 9201 has its optical port facing outward to allow theoptical connector to be plugged-in (see FIG. 10). Optionally, 4 remotehigh-power laser sources are provided externally via 4 fibers.Optionally, each laser can be split 8 ways to provide 32 100G/λ lanes.Optionally, each laser can be split 4 ways to provide 16 200G/λ lanes.In these options, 3.2 Tbit/s per light engine can be enabled.

FIG. 13 is a schematic diagram illustrating evolved integration schemesof moving light engines closer to a switch processor for reducinginterconnect reach distance in high-speed data communicationapplications according to some embodiments of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims. One of ordinary skill in the art would recognizemany variations, alternatives, and modifications. In some scenarios (Aand B) of the embodiment, the switch processor, no matter it isconfigured for PAM backplane reach (PKR) operation or extra-short-reach(XSR)/short reach (SR)/medium reach (MR) operation with each lightengine enabled with 100 Gbit/s per wavelength in one optical lane, canbe deployed alone on a switch substrate which is connected over acertain range of interconnect via gear box or retimer in-packaged withmultiple light engines on a separate line card. Optionally, the multiplelight engines are packaged four quadrants of optical-electricalsub-modules as shown in FIG. 4, FIG. 5, and FIG. 6 with each quadrantsub-module carrying 0.8 Tbit/s in 8 optical lanes. The certain range ofinterconnect includes long-range interconnect involving optical loss of35 dB or less in the scenario A, or medium-range interconnect involvingoptical loss of 25 dB or less, or short or extra-short range ofinterconnect involving optical loss of about 10 dB in the scenario Bwith each quadrant sub-module being improved to 1.6 Tbit/s in 8 opticallanes. The optical line interface can employ a PAM optical reach (POR)or equivalent protocol and the electrical host interface can include aPAM backplane reach (PKR) or equivalent protocol under a same setting ofline/host interface scheme for the scenarios of A and B.

In some other scenarios (C through F) of the embodiment, the switchprocessor is co-packaged with multiple light engines in a much closerdistance on a same switch substrate to form a co-packaged optical(switch) module which can be deployed to a network system in a singlerack chassis. No gear box or retimer is required while host FEC is usedin digital signal processing with 56 Gbaud electrical interface. Eachlight engine in the scenario C of the embodiment includes a siliconphotonics chip packaged with a TIA chip and modulation driver chip andstacked up with a digital signal processing (DSP) chip above or underthe silicon photonics chip. Optionally, the DSP chip is configured witha host interface, PCS/PMA layers, and a line interface for PAM opticalreach operation. The switch processor in this scenario is configuredwith DSP interface for 51.2T operation (see FIG. 11) disposed to acentral area of a 100 mm×100 mm switch substrate with each of 32 lightengines (each of 1.6 Tbit/s capacity) being distributed aroundperipheral regions of the switch substrate. Each light engine is limitedin a packaged chiplet of 10 mm×10 mm carrying 1.6 Tbit/s (see FIG. 12)including 4 in-packaged lasers and an externally coupledmultiplexer/demultiplexer optical interface integrated in an opticalconnector. The switch processor is connected with each of the 32 lightengines with a maximum distance of <50 mm via in-substrate interconnectin the switch substrate, yielding a power loss of <10 dB andcompatibility with the 51.2T extra-short-reach (XSR) or equivalentprotocol in data interconnect operation designed for the switchprocessor. Optionally, the switch processor can be connected with 16light engines of 3.2 Tbiy/s capacity to have 51.2T total datathroughput.

Alternatively, the scenarios D through F illustrate options of pushingthe light engine closer and closer to the processor with switchsubstrate or light engine substrate sizes being adjusted depending onindividual light engine chiplet die sizes. Each light engine chiplet isassumed to maintain 100 Gbit/s per wavelength in each optical lane. In aspecific embodiment, the light engine in the scenario D includes asilicon photonics chip and transimpedance amplifier with externallycoupled laser sources driven by analog driver and externalmultiplexer/demultiplexer optical interface to connect via on-boardfibers to an optical connector, while eliminating retimer functionwithin the light engine. Optionally, each light engine can be providedin a packaged chiplet form with a smaller individual die size.Optionally, the light engine includes an external SiGe-based modulationdriver with relatively higher power consumption. Optionally, the lightengine includes an external CMOS driver integrated in the switchprocessor to reduce the power consumption. The switch processor in thescenario D incorporates the DSP host interface only without FEC functionwhile implementing PAM optical reach. Optionally, the switch substratesize can be reduced further depending on individual light engine diesize and throughput setting per light engine. In an example, each lightengine still provides 1.6 Tbit/s, thus, the switch module still needs 32light engines to have 51.2 Tbit/s total throughput. In another example,each light engine is expanded to 3.2 Tbit/s, the co-packaged switchmodule needs just 16 light engines to have 51.2 Tbit/s total throughput.As the result, a maximum distance between the switch processor and oneof the multiple light engine chiplets co-packaged in the scenario D maybe reduced further. In an example, the distance is smaller than 15 mm topush even lower optical power loss in the XSR interconnect operation.

Additionally, in the scenario E, the light engine includes a siliconphotonics chip packaged with a TIA chip only while moving the modulationdriver into CMOS chip associated with the switch processor. Theindividual die size may be further reduced as the lasers and opticalinterface can all be coupled externally. The switch processor in thescenario E incorporates the DSP host interface to interact withelectrical host yet without FEC function and analog modulation driver tocontrol laser signals while implementing PAM optical reach. As theresult, a maximum distance between the switch processor and one of themultiple light engine chiplets co-packaged in the scenario E may bereduced even further. In an example, the distance is smaller than 5 mmto push even lower optical power loss in the extra-short-reach (XSR) orequivalent protocol in data interconnect operation and lower powerconsumption per module with the same 51.2 Tbit/s total throughput.

Furthermore, in the scenario F, the light engine is packaged byintegrating the silicon photonics chip with a Serializer/Deserializer(SerDes) block and a TIA chip in the packaged chiplet. The SerDes blockprovides data transmission over a single line or a differential pair inorder to minimize the number of I/O pins and interconnects. The dataspeed per line can be 56 Gb/s or 112 Gb/s. Optionally, the SerDes blockincludes digital encoding/decoding blocks. Accordingly, the switchprocessor in this scenario F employs Advanced Interface Bus (AIB) orparallel bus with packages to allow heterogeneous integration ofmultiple die into a single package to connect the analog front-end,signal pre-processing, to interface with Ser/Des block in each lightengine chiplet for ultra-short-reach (USR) interconnect operation. Inthe scenario F, between the switch processor and the multiple lightengine chiplets, an active Si interposer is inserted. The active Siinterposer extends the concept of Chip-on-Wafer-on-Substrate (CoWoS)technology based on a 2.5D or 3D integrated circuit employingthrough-silicon via (TSV) interposer-based packaging technology toprovide reticle matching the total module size and to hold the mainswitch processor die and all chiplet dies. Optionally, the active Siinterposer contains a grid of TSVs to connect IOs and supply plus activeregions to pass signals using buffers between two grids of conductivecontacts formed according to the design of the main processor die andmultiple dies of light engine chiplets as shown in FIG. 11 and FIG. 12.Optionally, the active Si interposer also can support connectingmultiple main dies on one package substrate. With the active Siinterposer, the light engine dies can be brought to he switch processoras close as <1 mm for establishing DSR-type interface.

FIG. 14 is an exploded view of all parts forming a packaged light enginechiplet as one of the multiple light engines in the co-packaged switchmodule according to an embodiment of the present invention. This diagramis merely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown, the packageincludes an assembly of part A through part E as a packaged light enginechiplet ready for being mounted on the same switch substrate withmultiple other light engine chiplets. The part A of the package is asub-assembly of the light engine chiplet, which is substantially same asthe sub-assembly 8000A described in FIG. 9. In a perspective view of thesub-assembly, it shows a lid member 8100 on top attached on a sub-modulesubstrate 8600 at bottom to enclose a light engine therein. Optionally,the sub-module substrate 8600 is a micro Land Grid Array (LGA) typesubstrate designated for mounting the light engine chiplet onto a modulesubstrate. Optionally, the light engine enclosed in the sub-assembly isconfigured as a multi-channel optical-electrical transceiver includingor coupling to multiple laser chips on a silicon photonics substrate toprovide multiple CWDM wavelength channels. Optionally, the light engineenclosed the sub-assembly is configured to be operated with a data ratecapacity of 1.6 Tbit/s or 200 Gbit/s for 8 optical lanes.

Referring to FIG. 14, the lid member 8100 is shown with more structuralelements that play respective roles to be assembled with other parts inthe package of the light engine chiplet. For example, the lid member8100 includes at least two straight side edges 8105 on two opposingsides naturally connected a front edge with an optical port 8110 and aback edge. Each side edge 8105 stands vertically on a ledge structure,i.e., a flat horizontal portion 8107 joined with a smaller verticalportion 8108. The ledge structure can be utilized by other parts forfixing the sub-assembly in the package.

The part B in the package of FIG. 14 is an interposer pad 8120configured to connect a micro LGA type substrate at its top side with aprinted circuit board below. In the package of FIG. 14, the interposerpad 8120 with an array of patterned holes 8125 is inserted below thesub-module substrate 8600 to provide capability to mate and de-mate thelight engine chiplet being surface-mounted on the co-packaged substrateor printed circuit board.

The part C in the package of FIG. 14 includes a plurality of connectionpins 8018 with small pitch size and low profile to provide connectionpaths for electrical signals between the light engine and circuits inthe switch substrate and other chips mounted on the switch substrate.The plurality of connection pins 8018 is arranged in a matrix arraydesigned to match the interposer pad 8120 compatible for high-speed (56Gbaud/s and higher) and high-power data communication. The matrix arrayof connection pins 8018 are respectively disposed at a matrix of throughholes in the part E which is configured as a socket base member 8010 atthe bottom of the package.

The part D in the package of FIG. 14 is a shaped metal wire 8020 forclamping the part A, i.e., a sub-assembly 8000A of the light enginechiplet, into the part E, the socket base member 8010. In particular,the socket member 8010 includes a flat plate 8011 with a matrix ofthrough holes 8013 compatible with the LGA-type interposer pad 8120 forforming proper electrical connections with the LGA-type substrate 8600of the sub-assembly 8000A. The matrix array of connection pins 8018 aredisposed into respective through holes 8013 in the flat plate 8011 sothat the interposer 8120 can be placed on top to form interconnect withrespective electrical contacts at the bottom side the sub-modulesubstrate 8600 as the sub-assembly of the light engine is disposed onthe interposer 8120 in the socket base member 8010. In addition, thematrix array of connection pins 8018 also form respective conductionpaths to connect the light engine with electrical contacts on a modulesubstrate (such as the switch substrate 9001 in FIG. 11) in aco-packaged optical module (such as CPO module 9000 in FIG. 11).

In the embodiment, the shaped metal wire 8020 is a single wire shapedwith at least a horizontal backside section 8026 extended tosubstantially entire length of the back wall of the socket base member8010, two bended back sections 8022 connected to respective ends of thehorizontal backside section 8026, two horizontal side sections 8027respectively connecting the two bended back sections 8022 to two bendedfront sections 8021. Each bended front section 8021 further is extendeddownward to a vertical section 8024 which is coupled to an end section8025 with a length much shorter than entire length of the front wallbended from the vertical section 8024 to horizontal direction along thefront wall of the socket base member 8010.

The part E, i.e., the socket base member 8010, is configured to havesome slot/notch structures at both the front wall and back wallrespectively matching the two bended front sections 8021 including thevertical section 8024 and the end section 8025 and two bended backsections 8022 including the horizontal backside section 8026. A bottomnotch (not visible in FIG. 14) formed in the back wall of the socketbase member 8010 is designed to hold the horizontal backside section8026 of the shaped metal wire 8020 so that the two bended back sections8022 are fitted in respective two back slots 8016. The bended front orback sections of the shaped metal wire 8020 may generate desired elasticforces depending on bending angle and mechanical tensile strength of themetal wire with a certain diameter. Accordingly, the two horizontal sidesections 8027 are forced to land on the two flat horizontal portion 8107of two side ledges of the lid member 8100 (provided that thesub-assembly 8000A is disposed in the socket base member 8010 in thepackage of FIG. 14). Furthermore, the two bended front sections 8021 ofthe shaped metal wire 8020 connect to the two end sections 8025respectively via two vertical sections 8024 so that the two end sectionsare respectively held by two bottom notches 8015 on the front wall ofthe socket base member 8010 to force the two horizontal side sections8027 on the two flat horizontal portion 8107 of the lid member 8100 toclamp the sub-assembly (part A of FIG. 14) of the light engine chipletin the socket base member 8010.

Moreover, the socket base member 8010 includes a couple of registrationpins 8012 designed to mate with a compatible registration holes in themodule substrate or printed circuit board (such as a switch substrate9001 in FIG. 11) to allow the packaged light engine chiplet beingsurface mounted in the co-packaged optical module. Optionally, the tworegistration pins 8012 are located at two diagonal positions at thebottom side of the socket base member 8010. As the socket base member8010 is mated with a sub-module site in the module substrate via theregistration pins 8012, the matrix array of connection pins 8018 alsohave their respective bottom contacts to form electrical connectionsbetween the light engine and the module substrate.

FIG. 15 shows a perspective view (part A) and a side view (part B) ofthe packaged light engine chiplet of FIG. 14 according to an embodimentof the present invention. This diagram is merely an example, whichshould not unduly limit the scope of the claims. One of ordinary skillin the art would recognize many variations, alternatives, andmodifications. As shown in part A of FIG. 15, the packaged light enginechiplet 9200 is a package assembled all the parts A through E shown inFIG. 14. In particular, the shaped metal wire 8020 (see part D of FIG.14) is applied to clamp the sub-assembly 8000A (part A of FIG. 14) ofthe light engine into the socket base member (part E) by pressing thehorizontal side section 8027 onto the flat horizontal portion 8107 ofthe ledge structure of the lid member 8100 and locking the end section8025 into the front-wall bottom notch 8015. Optionally, the front edge8105F of the sub-assembly 8000A of light engine chiplet includes anoptical port 8110. Optionally, the packaged light engine chiplet 9200substantially the same as each of the multiple light engines 9201co-packaged with a switch processor 9100 commonly on a switch substrate9001 to form the co-packaged optical module 9000 of FIG. 11.

The part B of FIG. 15 shows a side view of the same packaged lightengine chiplet 9200. In the embodiment, the vertical section 8024 of theshaped metal wire 8020 is positioned slightly ahead of the front edge8105F to leave a gap 8029 between them. This design allows a releasingmechanism to be applied for optional releasing the sub-assembly 8000Afrom the packaged light engine chiplet 9200 when the latter is one ofmultiple light engine chiplets 9201 disposed in the co-packaged opticalmodule to mate with the module substrate via the couple of registrationpins 8012. In the side view shown in the part B of FIG. 15, tworegistration pins 8012 can be seen. Optionally, the couple ofregistration pins 8012 are positioned along a diagonal direction of thesocket base member 8010. Also, a plurality of conduction pins 8018 withrespective bottom contacts can be seen in this side view diagram of thepackaged light engine chiplet 9200 to form electrical connectionsbetween the light engine and the module substrate.

FIGS. 16A-16C show a method of releasing a sub-assembly from thepackaged light engine chiplet of FIG. 15 according to an embodiment ofthe present invention. These diagrams are merely an example, whichshould not unduly limit the scope of the claims. One of ordinary skillin the art would recognize many variations, alternatives, andmodifications. In a partial view of a co-packaged optical module asshown in FIG. 16A, multiple packaged light engine chiplets 9201 aremounted on a module substrate 9001 (see FIG. 11). Each packaged lightengine chiplet 9201 includes a sub-assembly 8000A loaded in a socketbase member 8010 disposed along a peripheral edge of the modulesubstrate 9001 with a front edge facing the peripheral edge as indicatedby an optical port 8110. As seen in FIG. 16A the socket base member 8010of the packaged light engine chiplet 9201 is mounted in a corner site inthe module substrate 9001. Substantially like the light engine chiplet9200 shown in FIG. 15, two end sections 8025 of a metal wire 8020 arelocked respectively into two front-wall bottom notches 8015 to clamp thesub-assembly 8000A in the socket base member 8010. Optionally, thesub-assembly 8000A can be released from the socket base member 8010while the latter is still mated with the corner site in the modulesubstrate 9001.

In FIG. 16B, a removal tool 9300 is provided with two arms 9320connected in a U-shape piece. Each arm 9320 has a head member configuredas a top tip 9321 connected to a side tip 9324. The top tip 9321 has anextra length beyond an end facet 9323 of the side tip 9324 and a heightabove the arm 9320. The side tip 9324 has a length extended sideway at asame height from the arm 9320. Optionally, the removal tool 9300 isconfigured to be applied to the front edge of a packaged light enginechiplet 9201 disposed in its mating site on the module substrate 9001 torelease the sub-assembly 8000A clamped to the socket base member 8010.Optionally, the two arms 9320 are separated by a distance larger than awidth of the optical port 8110 so that the two head members can beengaged directly with the front edge. As the removal tool 9300 isengaged along direction 1 toward the front edge of the chiplet 9201 tohave the end facet 9323 against the front edge, the side tip 9324 isallowed to be inserted with an extra length against the vertical section8024 into the gap 8029 (see part B of FIG. 15). At the engaged position,the top tip 9321 of the respective head member has its bottom surface intouch with top surface of the lid member of the chiplet 9201. Then, theremoval tool 9300 is lifted upward along direction 2 from the joint partof the U-shape piece with the head member being substantially againstthe top surface and the side edge of the lid member of the chiplet 9201.The lift motion allows the side tip 9324 to push the vertical section8024 of the metal wire 8020 outward so that the end sections 8025 of themetal wire 8020 is released out of the locked position with thefront-wall bottom notches 8015 of the socket base member 8010. FIG. 16Cshows the released state of the metal wire 8020 with the end section8025 being no longer locked with the front-wall bottom notch 8015. Thesub-assembly 8000A of the light engine chiplet can then be released fromthe socket base member 8010 while the latter can remain being mated at acorresponding peripheral site of the module substrate 9001.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

What is claimed is:
 1. A co-packaged optical module comprising: asubstrate; a processor arranged on the substrate; and a plurality oflight engines mounted around the processor on the substrate usingmounting assemblies configured to attach the respective light engines tothe substrate, the light engines and the mounting assemblies disposedalong a perimeter of the substrate, including at corners of thesubstrate; each of the mounting assemblies comprising a socket, a metalclamp clamping a corresponding one of the light engines into the socket,and a plurality of pins which when mated with corresponding holes in thesubstrate cause peripheries of the mounting assemblies, including thelight engines, the sockets and the metal clamps, to be flush with theperimeter of the substrate.
 2. The co-packaged optical module of claim 1wherein the metal clamp includes a metal wire shaped to have a perimeterless than a perimeter of the socket and greater than a perimeter of thelight engines.
 3. The co-packaged optical module of claim 1 wherein eachof the light engines comprises a base substrate having electricalcontacts, and wherein each of the sockets comprises a base member havingan array of through holes, the co-packaged optical module furthercomprising: an interposer arranged below the base substrate of each ofthe light engines, the interposer having an array of patterned holesaligned with the electrical contacts of the base substrate; and an arrayof connecting pins having first ends extending through the patternedholes in the interposer and second ends extending via the through holesin the base member of the socket, the connecting pins connecting theelectrical contacts on the base substrate to electrical contacts on thesubstrate of the co-packaged optical module.
 4. The co-packaged opticalmodule of claim 1 wherein each of the light engines comprises: aplurality of interconnected substrates arranged in a stack, each of thesubstrates comprising circuits configured to process electrical signals;a silicon photonics substrate connected to one of the substrates in thestack, the silicon photonics substrate comprising optical circuitsconfigured to process optical signals; and a base substrate connected tothe silicon photonics substrate and having electrical contactsconfigured to connect to electrical contacts on the substrate of theco-packaged optical module.
 5. The co-packaged optical module of claim 4wherein each of the light engines comprises a lid member that enclosesthe substrates and the silicon photonics substrate, that is attached tothe base substrate, and that includes a port configured to receive andsecure an optical connector.
 6. The co-packaged optical module of claim5 wherein optical connector comprises a planar light circuit.
 7. Theco-packaged optical module of claim 4 wherein the silicon photonicssubstrate comprises one or more laser circuits providing a plurality ofwavelength division multiplexing communication channels.
 8. An opticalswitch comprising: a plurality of the co-packaged optical module ofclaim 1 arranged on a common substrate; an additional substrate arrangedbelow the common substrate, the additional substrate comprisingadditional circuits arranged on a bottom surface of the additionalsubstrate opposite to the common substrate; an interposer arrangedbetween the common substrate and the additional substrate, theinterposer comprising electrical contacts providing electricalconnections between the common substrate and the additional substrate; abase plate attached to the bottom surface of the additional substrate,the base plate including windows aligned with the additional circuits;and a heat sink arranged above the plurality of the co-packaged opticalmodule.
 9. The optical switch of claim 8 wherein: the base platecomprises a plurality of alignment pins that pass through correspondingholes in the additional substrate and the interposer; and a plurality offasteners pass through the heat sink and the additional substrate andlock into the base plate.